RDMA/mlx5: Add optional counters for RDMA_TX/RX_packets/bytes

RDMA/mlx5: Add optional counters for RDMA_TX/RX_packets/bytes

Add the following optional counters:
rdma_tx_packets,rdma_rx_bytes,rdma_rx_packets,rdma_tx_bytes.

Which counts all RDMA packets/bytes sent and received per link.

Note that since each direction packet and byte counter are shared,
the counter is only reset when both counters of that direction
are removed. But from user-perspective each can be enabled/disabled separately.

The counters can be enabled using:
sudo rdma stat set link rocep8s0f0/1 optional-counters rdma_tx_packets
And can be seen using:
rdma stat -j show link rocep8s0f0/1

Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Link: https://patch.msgid.link/9f2753ad636f21704416df64b47395c8991d1123.1741875070.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>